Communication control method

ABSTRACT

A communication control method is used in a mobile communication system that supports MDT (minimization of drive test). The communication control method has: a step (A) wherein a user terminal, which has established a connection with abase station, location information indicating the location of the user terminal to the base station based on an instruction from the base station; and a step (B) wherein the base station receiving the location information from the user terminal measures the throughput of communication with the user terminal.

TECHNICAL FIELD

The present invention relates to a mobile communication method and auser terminal used in a mobile communication system supporting MDT(Minimization of Drive Test) defined in the 3GPP (3rd GenerationPartnership Project) standard.

BACKGROUND ART

In a mobile communication system, a radio communication environmentaround a base station changes when a buildings is constructed near thebase station or installation conditions of its neighboring base stationschange. Hence, it has been a common practice to perform a drive testwhere an operator uses a measurement vehicle carrying measurementequipment to measure states of signals received from a base station andcollect measured data.

Although such measurement and collection is useful in optimizingcoverage of the base station, for example, it has a problem of requiringa large number of man-hours and high cost. In view of this problem, 3GPP(3rd Generation Partnership Project) which is a standardization projectof mobile communication systems is formulating a specification of MDT(Minimization of Drive Tests) for automating the measurement andcollection by use of a user terminal held by a user (refer to Non-patentdocuments 1 and 2).

PRIOR ART DOCUMENT Non-Patent Document

-   Non-patent document 1: 3GPP TR 36.805 V9.0.0-   Non-patent document 2: 3GPP TR 37.320 V10.2.0

SUMMARY OF THE INVENTION

It is important to verify not only received signal state from a basestation but also QoS (Quality of Service) of communications with thebase station in order to improve user experience besides the coverageoptimization.

However, there is a problem that the current MDT specification has nomechanism for verifying the QoS.

Thus, the present invention provides a communication control methodcapable of verifying the QoS by MDT manner.

A communication control method according to the present invention isused in a mobile communication system supporting MDT (Minimization ofDrive Test). The communication control method includes: a step A oftransmitting location information indicating a location of a userterminal establishing a connection with a base station, from the userterminal to the base station, based on an instruction from the basestation; and a step B of measuring, by the base station receiving thelocation information from the user terminal, a throughput ofcommunication with the user terminal.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows a mobile communication system of an embodiment of thepresent invention.

FIG. 2 is a block diagram of an eNB of the embodiment of the presentinvention.

FIG. 3 is a block diagram of a UE of the embodiment of the presentinvention.

FIG. 4 shows basic operation pattern of the mobile communication systemof the embodiment of the present invention.

FIG. 5 shows operation pattern 1 of the mobile communication system ofthe embodiment of the present invention.

FIG. 6 shows operation pattern 2 of the mobile communication system ofthe embodiment of the present invention.

FIG. 7 shows operation pattern 3 of the mobile communication system ofthe embodiment of the present invention.

FIG. 8 shows operation pattern 4 of the mobile communication system ofthe embodiment of the present invention.

FIG. 9 shows operation pattern 5 of the mobile communication system ofthe embodiment of the present invention.

FIG. 10 shows operation pattern 6 of the mobile communication system ofthe embodiment of the present invention.

DESCRIPTION OF THE EMBODIMENTS

An embodiment of the present invention will be described with referenceto the drawings. In the following drawings of the embodiment, same orsimilar reference signs denote same or similar portions.

Summary of Embodiment

A communication control method according to an embodiment is used in amobile communication system supporting MDT (Minimization of Drive Test).The communication control method includes: a step A of transmittinglocation information indicating a location of a user terminalestablishing a connection with a base station, from the user terminal tothe base station, based on an instruction from the base station; and astep B of measuring, by the base station receiving the locationinformation from the user terminal, a throughput of communication withthe user terminal. This enables QoS verification about how throughput isobtained at which location, thereby it is possible to contribute theoptimization for improving user experience. Such QoS verificationenables to identify areas where QoS deteriorates.

In the embodiment, in the step B, the base station measures a throughputof communication with the user terminal per unit time. The communicationcontrol method further includes a step C of associating the locationinformation received from the user terminal with the throughput measuredin the unit time corresponding to a reception timing of the locationinformation. This enables to identify about how throughput is obtainedat which location, with a high degree of accuracy.

In the embodiment, in the step B, the base station individually measuresan uplink throughput in the communication with the user terminal and adownlink throughput in the communication with the user terminal when thebase station receives the location information from the user terminal.This enables QoS verification for each of uplink and downlink.Especially, it is useful for a mobile communication system adaptingcommunication schemes (radio access scheme) are different in uplink anddownlink.

In the embodiment, in the step B, the base station measures a throughputper user terminal when the base station receives the locationinformation from each of plural user terminals establishing connectionswith the base station. This enables to QoS verification for each ofplural user terminals.

In the embodiment, in the step B, the base station measures a throughputper radio access bearer of the user terminal when the base stationreceives the location information from the user terminal. The each radioaccess bearer is subject to QoS control based on the QoS characteristicof radio access bearer. Therefore, this enables QoS verification aboutwhether the QoS characteristic is satisfied for each radio accessbearer.

In the embodiment, the method further includes: a recording step ofrecording location information indicating a geographical location of auser terminal by the user terminal in a connected state, during a periodin which throughput of communication between the user terminal and anetwork is deteriorated; and a reporting step of reporting the locationinformation recorded in the recording step to the network by the userterminal after restoration of the throughput. Here, throughput mayindicate any of uplink throughput and downlink throughput.

In the embodiment, the method further includes a notification step ofnotifying the user terminal of a network time by the network whenperforming initial setting for in the user terminal.

In the embodiment, the method further includes: a deteriorationdetection step of detecting the deterioration in the throughput by thenetwork; and a request transmission step of sending the user terminal arequest for recording the location information from the network, upondetection of the deterioration in the throughput in the deteriorationdetection step. In the recording step, the user terminal startsrecording of the location information in response to the recordingrequest from the network.

In the embodiment, the network notifies the user terminal of a networktime in the request transmission step.

In the embodiment, the method further includes: a restoration detectionstep of detecting the restoration of the throughput by the network; anda request transmission step of sending the user terminal a request forreporting the location information from the network, upon detection ofthe restoration of the throughput in the restoration detection step. Inthe recording step, the user terminal ends recording of the locationinformation upon receipt of the reporting request from the network, andin the reporting step, the user terminal reports the locationinformation recorded in the recording step to the network in response tothe reporting request from the network.

In the embodiment, the method further includes a deterioration detectionstep of detecting the deterioration in the throughput by the userterminal. In the recording step, the user terminal starts recording ofthe location information upon detection of the deterioration in thethroughput in the deterioration detection step.

In the embodiment, the method further includes: a step of sending thenetwork a request for notification of a network time from the userterminal upon detection of the deterioration in the throughput in thedeterioration detection step; and a step of notifying the user terminalof a network time by the network in response to the notification requestfrom the user terminal.

In the embodiment, the method further includes a restoration detectionstep of detecting the restoration of the throughput by the userterminal. In the recording step, the user terminal ends recording of thelocation information upon detection of the restoration of the throughputin the restoration detection step, and in the reporting step, the userterminal reports the location information recorded in the recording stepto the network upon detection of the restoration of the throughput inthe restoration detection step.

In the embodiment, in the recording step, the user terminal records timeinformation including the network time and a relative time based on thenetwork time, in association with the location information, and in thereporting step, the user terminal reports the location information andthe time information recorded in the recording step to the network.

In the embodiment, the method further includes: a step of recording ameasurement result of the throughput in association with a network timeby the network; and a step of associating the measurement result of thethroughput with the location information according to the timeinformation by the network, after receiving the location information andthe time information reported in the reporting step.

In the embodiment, the network (the eNB, MME, or OAM) associateslocation information and a measurement result of the throughput assumedto have been acquired in the same time period, according to acombination of the location information and the time informationincluded in the report from the user terminal, and a combination of themeasurement result of the throughput and the network time recorded bythe network.

In the embodiment, in the recording step, the user terminal records themeasurement result of the throughput and the time information includingthe network time and the relative time based on the network time, inassociation with the location information, and in the reporting step,the user terminal reports the measurement result of the throughput, thelocation information, and the time information recorded in the recordingstep to the network.

In the embodiment, the deterioration in the throughput refers to a statewhere the throughput becomes lower than a predetermined threshold, or astate where the throughput becomes lower than a throughput rangeestimated from the number of resource blocks and an MCS (Modulation andCoding Scheme) applied to communication between the user terminal andthe network.

Configuration of Mobile Communication System

FIG. 1 shows the mobile communication system of the embodiment. Themobile communication system has a configuration based on 3GPP standard(especially, LTE). In the mobile communication system, as radio accessscheme, SC-FDMA scheme is applied to an uplink and OFDMA scheme isapplied to a downlink.

As shown in FIG. 1, the mobile communication system includes multiplebase stations (evolved Node-B: eNB) and a user terminal (User Equipment:UE) connecting to one of the eNBs. The multiple eNBs form an E-UTRAN(Evolved-UMTS Terrestrial Radio Access Network) which is a radio accessnetwork of LTE. Each eNB manages one or multiple cells. A cell isidentified by a cell ID. A UE is allocated a radio resource by a cell towhich it is connected (called serving cell) when it is in a connected(RRC Connected) state. In the mobile communication system, an X2interface which is a logical communication channel for interconnectingneighboring eNBs is established. Additionally, an S1 interface which isa logical communication channel for connecting with an EPC (EvolvedPacket Core) being a core network of LTE is established between the EPCand the eNB, as well as between the EPC and the eNB. The EPC includes anMME (Mobility Management Entity) and an S-GW (Serving Gateway). The MMEmanages a TA and/or a cell in which the UE is located, and performsvarious kinds of mobility management for the UE. The S-GW controlstransfer of user data received by and sent from the UE. The mobilecommunication system further includes an OAM (Operation and Maintenance)for maintenance and monitoring of an E-UTRAN 10. In the embodiment, theE-UTRAN, the EPC, and the OAM form a network (NW).

Each UE in connected state establishes one or more radio access bearerswith eNB. The each radio access bearer is subject to QoS control basedon the QoS characteristic corresponding to the radio access bearer, innetwork (especially, in eNB).

FIG. 2 is a block diagram of the eNB. As shown in FIG. 2, the eNBincludes an antenna 101, a radio communication unit 110, a networkcommunication unit 120, a storage 130, and a controller 140. The antenna101 is used for transmission and reception of radio signals. The radiocommunication unit 110 is formed of a radio frequency (RF) circuit, abaseband (BB) circuit and the like, for example, and exchanges radiosignals via the antenna 101. The network communication unit 120 performsinter-base station communication with a neighboring eNB over the X2interface. The network communication unit 120 also communicates with theEPC over the S1 interface. The storage 130 stores therein various kindsof information used for control and the like of the eNB. The controller140 controls various functions (to be described later in detail) of theeNB.

FIG. 3 is a block diagram of the UE. As shown in FIG. 3, the UE includesan antenna 201, a radio communication unit 210, a location informationacquisition unit 220, a storage 230, and a controller 240. The antenna201 is used for transmission and reception of radio signals. The radiocommunication unit 210 is formed of an RF circuit, a BB circuit and thelike, for example, and exchanges radio signals via the antenna 201. Thelocation information acquisition unit 220 includes a GPS receiver, forexample, and outputs location information based on received GPS signalsto the controller 240. The storage 230 stores therein various kinds ofinformation used for control and the like of the UE. The controller 240controls various functions (to be described later in detail) of the UE.

Operation of Mobile Communication System

Hereinafter, a description is given of operations of the mobilecommunication system of the embodiment.

First of all, a description is given of a basic operation of the mobilecommunication system of the embodiment. FIG. 4 shows the basic operationpattern of the mobile communication system. In the initial state of thisoperation, the UE is a state connected to the eNB (connected state). MDTwhich is applied to the connected state UE is called Immediate-type MDT(Immediate MDT).

As shown in FIG. 4, is step S11, the eNB performs initial setting forcommunicating with the UE or performs initial setting for MDT. Theinitial setting includes instruction information for instructing atransmission (a report) of location information indicating thegeographic location of the UE. The UE receives initial settinginformation including the instruction information.

In step S12, the eNB starts the measurement of throughput ofcommunication with the UE. The throughput is measured at a layer 2 (L2)of the eNB. The eNB measures the throughput of communication with the UEper unit time. The eNB may individually measure an uplink throughput inthe communication with the UE and a downlink throughput in thecommunication with the UE. The eNB may measure the throughput per UEwhen the eNB receives the location information from each of plural UEsestablishing connections with the eNB. Furthermore, the eNB may measurethe throughput per radio access bearer of the UE. The throughput ismeasured for QoS verification. In addition to the throughput, asverification parameter of QoS, packet delay and latency (packet delayand loss rate) are exists.

In step S13, the UE starts the acquisition of location information basedon the instruction information received from the eNB. The UE mayperiodically acquire the location information, or may acquire thelocation information by a trigger of occurrence of predetermined event.

In step S14, the UE transmits the location information acquired in thestep S13. The eNB receives the location information from the UE.

In step S15, the eNB associates the location information received fromthe UE in the step S14 with the throughput measured in the unit timecorresponding to the reception timing of the location information, andthe records them. The information recorded at the eNB is notified toOAM, for example.

The base station measures the throughput and the user terminal acquiresand transmits (reports) the location information, for the followingreasons. The location information acquired by the user terminal is highaccuracy and high reliability. Therefore, it is possible to identifyareas where the QoS is deteriorated, with high accuracy. On the otherhand, the network performs wrong optimization (e.g. schedulingoptimization) if the location information is not reliable, and then QoSof entire system may be deteriorated.

Although the basic operation of the embodiment is described above,hereinafter, a description is given of improved operations of the mobilecommunication system of the embodiment.

(1) Operation Pattern 1

FIG. 5 shows operation pattern 1 of the mobile communication system. Inthe initial state in FIG. 5, the UE is connected to the eNB.

As shown in FIG. 5, in step S101, the eNB performs initial setting forcommunicating with the UE or performs initial setting for MDT. In theinitial setting, the eNB may notify the UE of a network time. Thenetwork time is a time managed in the network. Upon receipt of thenetwork time, the UE starts a relative-time timer. The relative-timetimer is configured to count the time elapsed (relative time) from thereceived network time.

In step S102, the eNB starts measurement and recording of throughput ofcommunication between itself and the UE. Specifically, the eNB measuresthroughput of communication between itself and the UE, and records themeasurement result in association with the network time.

In step S103, the eNB detects deterioration in throughput ofcommunication between itself and the UE. Deterioration in throughputrefers to a state where the throughput becomes lower than apredetermined threshold, or where the throughput becomes lower than athroughput range estimated from the number of resource blocks and an MCS(Modulation and Coding Scheme) applied to the communication between theUE and the eNB. An MCS is defined by a combination of a modulationscheme and a coding scheme. A resource block is a unit of radio resourcedivided in the frequency direction. The eNB allocates one or multipleresource blocks to the UE.

In step S104, upon detection of the deterioration in throughput ofcommunication between itself and the UE, the eNB sends the UE a requestfor recording location information. In the recording request, the eNBmay notify the UE of the network time. Upon receipt of the network time,the UE starts the relative-time timer. The recording request may alsoinclude information specifying a time interval for recording locationinformation.

In step S105, in response to the location information recording requestfrom the eNB, the UE starts acquisition and recording of locationinformation. Specifically, the UE acquires location informationindicating its own geographical location, and records the acquiredlocation information in association with time information (network timeand relative time). Here, relative time is that counted by therelative-time timer at the time of acquiring the location information.

In step S106, the eNB detects restoration of throughput of communicationbetween itself and the UE. Restoration of throughput refers to a statewhere the throughput becomes higher than the predetermined threshold, orwhere the throughput becomes higher than the throughput range estimatedfrom the number of resource blocks or the MCS applied to thecommunication between the UE and the eNB.

In step S107, upon detection of the restoration of throughput ofcommunication between itself and the UE, the eNB sends the UE a requestfor reporting location information.

In step S108, in response to the location information reporting requestfrom the eNB, the UE ends recording of location information.

In step S109, in response to the location information reporting requestfrom the eNB, the UE sends the eNB a report including at least one ofrecorded combinations of location information and time information.

In step S110, the eNB, MME, or OAM associates location information and athroughput measurement result assumed to have been acquired in the sametime period. The two are associated according to a combination oflocation information and time information included in the report fromthe UE, and a combination of throughput measurement result and networktime recorded by the eNB. As an association method, the UE and eNB (aswell as a network entity associating the location information andmeasurement result) may each have a dedicated identifier which is addedto a header or the like of the location information and measurementresult, so that they may later be used in associating the locationinformation and the measurement result. Alternatively, the network mayidentify the UE having sent the location information or measurementresult according to the IP address, MAC address, or an allocated C-RNTIof the UE, to thereby associate the location information and themeasurement result later.

The reason why the low throughput condition is targeted is describedbelow. Although identification of overmuch throughput areas is onepurpose of QoS verification, such areas do not directly influences theuser experience. Therefore, it is preferable to target the lowthroughput condition.

(2) Operation Pattern 2

FIG. 6 shows operation pattern 2 of the mobile communication system.Although in operation pattern 1 the eNB detects throughput restoration,in this operation pattern, the UE detects throughput restoration. Notethat descriptions of parts overlapping with the aforementioned operationpattern are omitted as appropriate.

As shown in FIG. 6, in step S201, the eNB performs initial setting forcommunicating with the UE or performs initial setting for MDT. In theinitial setting, the eNB may notify the UE of a network time.

In step S202, the eNB starts measurement and recording of throughput ofcommunication between itself and the UE. Specifically, the eNB measuresthroughput of communication between itself and the UE, and records themeasurement result in association with the network time.

In step S203, the eNB sends the UE a request for measuring throughput.In the measurement request, the eNB may notify the UE of the networktime.

In step S204, in response to the measurement request from the eNB, theUE starts measurement of throughput of communication between itself andthe eNB.

In step S205, the eNB detects deterioration in throughput ofcommunication between itself and the UE.

In step S206, upon detection of the deterioration in throughput ofcommunication between itself and the UE, the eNB sends the UE a requestfor recording location information. In the recording request, the eNBmay notify the UE of the network time.

In step S207, in response to the location information recording requestfrom the eNB, the UE starts acquisition and recording of locationinformation. Specifically, the UE acquires location informationindicating its own geographical location, and records the acquiredlocation information in association with time information (network timeand relative time).

In step S208, the UE detects restoration of throughput of communicationbetween itself and the eNB.

In step S209, upon detection of the restoration of throughput ofcommunication between itself and the eNB, the UE ends recording oflocation information.

In step S210, upon detection of the restoration of throughput ofcommunication between itself and the eNB, the UE sends the eNB a reportincluding at least one of recorded combinations of location informationand time information.

In step S211, the eNB, MME, or OAM associates location information and athroughput measurement result assumed to have been acquired in the sametime period. The two are associated according to a combination oflocation information and time information included in the report fromthe UE, and a combination of throughput measurement result and networktime recorded by the eNB.

(3) Operation Pattern 3

FIG. 7 shows operation pattern 3 of the mobile communication system.Although in operation patterns 1 and 2 the eNB records the throughputmeasurement result, in this operation pattern, the UE records thethroughput measurement result. In addition, in this operation pattern,the UE detects throughput restoration. Note that descriptions of partsoverlapping with the aforementioned operation patterns are omitted asappropriate.

As shown in FIG. 7, in step S301, the eNB performs initial setting forcommunicating with the UE or performs initial setting for MDT. In theinitial setting, the eNB may notify the UE of a network time.

In step S302, the eNB starts measurement of throughput of communicationbetween itself and the UE.

In step S303, the eNB sends the UE a request for recording throughput.In the recording request, the eNB may notify the UE of the network time.

In step S304, in response to the throughput recording request from theeNB, the UE starts measurement and recording of throughput ofcommunication between itself and the eNB. Specifically, the eNB measuresthroughput of communication between itself and the UE, and records themeasurement result in association with time information (network timeand relative time). Note, however, that this recording is not essential,and may be omitted.

In step S305, the eNB detects deterioration in throughput ofcommunication between itself and the UE.

In step S306, upon detection of the deterioration in throughput ofcommunication between itself and the UE, the eNB sends the UE a requestfor recording location information. In the recording request, the eNBmay notify the UE of the network time.

In step S307, in response to the location information recording requestfrom the eNB, the UE starts acquisition and recording of locationinformation. Specifically, the UE acquires location informationindicating its own geographical location, and records the acquiredlocation information in association with the throughput measurementresult and time information (network time and relative time).

In step S308, the UE detects restoration of throughput of communicationbetween itself and the eNB.

In step S309, upon detection of the restoration of throughput ofcommunication between itself and the eNB, the UE ends recording oflocation information.

In step S310, upon detection of the restoration of throughput ofcommunication between itself and the eNB, the UE sends the eNB a reportincluding at least one of combinations of throughput measurement result,location information, and time information.

(4) Operation Pattern 4

FIG. 8 shows operation pattern 4 of the mobile communication system.Although in operation patterns 1 to 3 the eNB detects throughputdeterioration, in this operation pattern, the UE detects throughputdeterioration. Note that descriptions of parts overlapping with theaforementioned operation patterns are omitted as appropriate.

As shown in FIG. 8, in step S401, the eNB performs initial setting forcommunicating with the UE or performs initial setting for MDT. In theinitial setting, the eNB may notify the UE of a network time.

In step S402, the eNB starts measurement and recording of throughput ofcommunication between itself and the UE. Specifically, the eNB measuresthroughput of communication between itself and the UE, and records themeasurement result in association with the network time.

In step S403, the eNB sends the UE a request for measuring throughput.In the measurement request, the eNB may notify the UE of the networktime.

In step S404, in response to the measurement request from the eNB, theUE starts measurement of throughput of communication between itself andthe eNB.

In step S405, the UE detects deterioration in throughput ofcommunication between itself and the eNB.

In step S406, if the network time is not received from the eNB, the UEsends the eNB a request for notification of the network time.

In step S407, in response to the network time notification request, theeNB notifies the UE of the network time.

In step S408, the UE starts acquisition and recording of locationinformation. Specifically, the UE acquires location informationindicating its own geographical location, and records the acquiredlocation information in association with time information (network timeand relative time).

In step S409, the eNB detects restoration of throughput of communicationbetween itself and the UE.

In step S410, upon detection of the restoration of throughput ofcommunication between itself and the UE, the eNB sends the UE a requestfor reporting location information.

In step S411, in response to the location information reporting requestfrom the eNB, the UE ends recording of location information.

In step S412, in response to the location information reporting requestfrom the eNB, the UE sends the eNB a report including at least one ofrecorded combinations of location information and time information.

In step S413, the eNB, MME, or OAM associates location information and athroughput measurement result assumed to have been acquired in the sametime period. The two are associated according to a combination oflocation information and time information included in the report fromthe UE, and a combination of throughput measurement result and networktime recorded by the eNB.

(5) Operation Pattern 5

FIG. 9 shows operation pattern 5 of the mobile communication system. Inthis operation pattern based on operation pattern 4, the UE records thethroughput measurement result. Note that descriptions of partsoverlapping with the aforementioned operation patterns are omitted asappropriate.

As shown in FIG. 9, in step S501, the eNB performs initial setting forcommunicating with the UE or performs initial setting for MDT. In theinitial setting, the eNB may notify the UE of a network time.

In step S502, the eNB starts measurement of throughput of communicationbetween itself and the UE.

In step S503, the eNB sends the UE a request for recording throughput.In the recording request, the eNB may notify the UE of the network time.

In step S504, the UE starts measurement and recording of throughput ofcommunication between itself and the eNB. Specifically, the UE measuresthroughput of communication between itself and the eNB, and records themeasurement result in association with time information (network timeand relative time).

In step S505, the UE detects deterioration in throughput ofcommunication between itself and the eNB.

In step S506, if the network time is not received from the eNB, the UEsends the eNB a request for notification of the network time.

In step S507, in response to the network time notification request, theeNB notifies the UE of the network time.

In step S508, the UE starts acquisition and recording of locationinformation. Specifically, the UE acquires location informationindicating its own geographical location, and records the acquiredlocation information in association with the throughput measurementresult and time information (network time and relative time).

In step S509, the eNB detects restoration of throughput of communicationbetween itself and the UE.

In step S510, upon detection of the restoration of throughput ofcommunication between itself and the UE, the eNB sends the UE a requestfor reporting location information.

In step S511, in response to the location information reporting requestfrom the eNB, the UE ends recording of location information.

In step S512, in response to the location information reporting requestfrom the eNB, the UE sends the eNB a report including at least one ofcombinations of throughput measurement result, location information andtime information.

(6) Operation Pattern 6

FIG. 10 shows operation pattern 6 of the mobile communication system. Inthis operation pattern based on operation pattern 5, the UE detectsthroughput restoration. Note that descriptions of parts overlapping withthe aforementioned operation patterns are omitted as appropriate.

As shown in FIG. 10, in step S601, the eNB performs initial setting forcommunicating with the UE or performs initial setting for MDT. In theinitial setting, the eNB may notify the UE of a network time.

In step S602, the eNB sends the UE a request for recording throughput.In the recording request, the eNB may notify the UE of the network time.

In step S603, the UE starts measurement and recording of throughput ofcommunication between itself and the eNB. Specifically, the UE measuresthroughput of communication between itself and the eNB, and records themeasurement result in association with time information (network timeand relative time). Note, however, that this recording is not essential,and may be omitted.

In step S604, the UE detects deterioration in throughput ofcommunication between itself and the eNB.

In step S605, if the network time is not received from the eNB, the UEsends the eNB a request for notification of the network time.

In step S606, in response to the network time notification request, theeNB notifies the UE of the network time.

In step S607, the UE starts acquisition and recording of locationinformation. Specifically, the UE acquires location informationindicating its own geographical location, and records the acquiredlocation information in association with the throughput measurementresult and time information (network time and relative time).

In step S608, the UE detects restoration of throughput of communicationbetween itself and the eNB.

In step S609, upon detection of the restoration of throughput ofcommunication between itself and the eNB, the UE ends recording oflocation information.

In step S610, the UE sends the eNB a report including at least one ofcombinations of throughput measurement result, location information andtime information.

This application claims the benefit of priority from U.S. ProvisionalApplication No. 61/556,407 (filed on Nov. 7, 2011), the entire contentsof which are incorporated herein by reference.

INDUSTRIAL APPLICABILITY

As described, the present invention enables QoS verification by MDT, andtherefore is useful in radio communications field such as mobilecommunications.

The invention claimed is:
 1. A communication control method used in amobile communication system supporting immediate MDT (Minimization ofDrive Test), comprising: receiving an instruction from a base station,by a user terminal being in a radio resource control (RRC) connectedstate in a cell of the base station, wherein the instruction includestime interval information that specifies periodicity for the immediateMDT; acquiring, by the user terminal being in the RRC connected state,location information indicating a location of the user terminal based onthe instruction from the base station; measuring, by the user terminal,an uplink packet delay of uplink communication with the base station,wherein radio access bearers of the user terminal are associated withQuality of Service (QoS) characteristics to perform QoS control, and theuser terminal periodically measures the uplink packet delay per radioaccess bearer; comparing, by the user terminal being in the RRCconnected state, the measured uplink packet delay with a packet delaythreshold value; determining, by the user terminal being in the RRCconnected state, whether to transmit a report to the base station basedon result of the comparing, the report indicating the measured uplinkpacket delay wherein the user terminal continues reporting operations inaccordance with the instruction during the RRC connected state even whenthe packet delay threshold value is satisfied; and transmitting thereport including the location information to the base station based onresult of the determining.
 2. The communication control method accordingto claim 1, wherein the user terminal measures the uplink packet delayper radio access bearer per unit time.
 3. A user terminal thatestablishes a connection with a base station in a mobile communicationsystem supporting immediate MDT (Minimization of Drive Test),comprising: a controller containing a processor, and configured to causethe user terminal to execute processes of: receiving an instruction froma base station, by the user terminal being in a radio resource control(RRC) connected state in a cell of the base station, wherein theinstruction includes time interval information that specifiesperiodicity for the immediate MDT; acquiring, while in the RRC connectedstate, location information indicating a location of the user terminalbased on the instruction from the base station; measuring an uplinkpacket delay of uplink communication with the base station, whereinradio access bearers of the user terminal are associated with Quality ofService (QoS) characteristics to perform QoS control, and the userterminal periodically measures the uplink packet delay per radio accessbearer; comparing, while in the RRC connected state, the measured uplinkpacket delay with a packet delay threshold value; determining, while inthe RRC connected state, whether to transmit a report to the basestation based on result of the comparing, the report indicating themeasured uplink packet delay, wherein the user terminal continuesreporting operations in accordance with the instruction during the RRCconnected state even when the packet delay threshold value is satisfied;and transmitting the report including the location information to thebase station based on result of the determining.
 4. The user terminalaccording to claim 3, wherein in the process of measuring, thecontroller is configured to measure an uplink latency per radio accessbearer.